The field of lubricating internal combustion engines is constantly striving to develop novel lubricant compositions for increasing the lubricity of lubricant oils, reducing the wear rate of the metals being lubricated, and increasing the load bearing properties between the various surfaces within the engine.
Liquid crystalline compositions, by and large, have not attracted much attention within the field of lubrication as have more conventional chemical additives. Among the disclosures known to the present inventors are the following:
U.S. Pat. No. 4,781,849 to G. Biresaw et al. describes a metalworking lubricant which comprises a lyotropic liquid crystal and contained certain defined amounts of natural or synthetic oil, water-soluble surfactant, organic cosurfactant comprising a C.sub.4 -C.sub.12 1,2-alkanediol, and water containing less than about 1 wt % dissolved inorganic salts.
European Patent Publication No. 92,682 describes the use of certain liquid crystalline compounds, such as cyanobiphenyl, in a watch lubricant rather than in a lubricant for an internal combustion engine.
The addition of such liquid crystalline compounds as cholesterol caproate (Chemical Abstracts, 1983, Vol.99, 107765z) and certain benzoic acid derivatives (Chemical Abstracts, 1985, Vol. 102, 187599s) to lubricating oils was studied by A. P. Gribailo and coworkers and reported by B. I Kupchinov et al. in Tribology International, February 1991, Vol. 24, No.1, pp. 25-28 along with their work on using industrially produced thermotropic liquid crystals.